1. Field of Industrial Application
The present invention relates to a field emission display device which is arranged to emit light by exciting a fluorescent material with electron rays and more particularly to the field emission display device which is driven at a low anode voltage.
2. Description of the Related Art
As a very thin display device, the so-called field emission display device has been proposed wherein a lot of minute cathode electrodes (micro tips) served as an electron emitting source are formed on each pixel area so that fluophors provided on an anode electrode side are made active by exciting the micro tips of the corresponding pixel areas to a given electric signal.
The field emission display device includes as basic components a cathode electrode, an insulating layer formed on the cathode electrode, gate lines formed on the insulating layer and having lots of openings (gates) formed therein, and micro tips serving as minute cold cathodes located in lots of holes passing from the cathode electrode formed in the insulating layer to the gate line, the micro tips corresponding to the gates. That is, the pixels of the field emission display are composed of lots of electron emitting sources each of which has a cathode electrode, an insulating layer, gate lines, and micro tips.
On the anode electrode side of the display device arranged as described above, as shown in FIG. 1, a fluorescent screen 21 is formed facing the cathode electrode on the lower surface of the anode electrode 20 composed of a glass material. On the fluorescent screen 21, a fluorescent agent is coated in a bandlike manner so that the fluorescent agent bands are formed in parallel to the cathode lines.
On the fluorescent screen 21, fluophors 22 excited by electrons for emitting light and black masks 23 are formed on the side facing to the cathode electrode. Hence, on the lower surface of this fluorescent screen 21, the fluophors 22 are formed and excited by electrons so that this surface of the fluorescent screen 21 is served as the fluorescent screen 21 of the display device 1.
The black masks 23 are located to section lots of fluophors 22. The black masks 23 serve to section the fluophors 22 in a manner to correspond to R, G and B.
The display device arranged as described above is driven as below.
At first, a voltage Vc is applied to the cathode electrode. By applying a larger voltage Vg than Vc to the gate, the cold cathodes are excited to emit electrons. The emitted electrons are accelerated by the anode electrode and then reach the fluophors coated on the anode so that the fluophors operate to be luminous.
In the display device, however, the fluophor 22 formed on the anode electrode emit light onto the cathode electrode side when the electrons emitted from the cathode electrode excites the fluophors 22. Hence, the application of light onto the cathode electrode results in inhibiting contribution of part of emission to the emission from the screen.
Further, the fluophors 22 are formed as opposed to the electron emitting source and are formed on the anode electrode side of the substrate 20. Hence, the fluophor 22 is stripped off the substrate 20 and thereby gas is discharged through the stripped portion. This disadvantageously brings about an electric discharge between the anode electrode and the cathode electrode, which leads to lack of reliability of the display device.